The classes have different spell books and even the classes with the same books might not be allowed to use them all. (Also, the effects and costs of spells are different for different classes.)
Healing spells are available to priests and paladins.
Also, I think there was a minor healing spell for rogues, but I am not sure.

There is also a new branch of the game with a different distribution of spells and even more special class-related books.

It's rangers that get CLW in current release vanilla. Rogues get improved object detection.

What Mondkalb said. Stay away from big groups of monsters. And dont bother to kill jellies and molds, unless they are in your way. They have lousy EXP and the unmoving ones have no drops. So a jelly pit is a double no.

The classes have different spell books and even the classes with the same books might not be allowed to use them all. (Also, the effects and costs of spells are different for different classes.)
Healing spells are available to priests and paladins.
Also, I think there was a minor healing spell for rogues, but I am not sure.

There is also a new branch of the game with a different distribution of spells and even more special class-related books.

Oh, I thought mages got all the magic spells.

So is the 'basic' book only for sale in case you lose the one you start with?

If you can afford them, go for it. Carrying more than 50K gold has rapidly diminishing returns.
Here are the necessary purchases, later in the game:
* CCW - As much as you can feasible carry
* Staff of teleportation (or two if you can carry a second. )
* All town spellbooks, possibly dropping one later in the game
* recall -- stack of ~5. It's no good to get stuck without after getting fire damage.
* Phase door- stack of 10-15
* !Heroism-stack of 3 to 5 (leave this if inventory is tight. But it really helps your archery, and fear is bad for all classes in any case.)
Optional:
* Restore life
Stuff from black market (always get these if available)
* scroll of teleportation--become less useful after dl ~50.
* scroll of teleport level
* potion of healing
* scroll of *destruction*
* wand of teleport other @15000GP
* rod of teleport other
Black market (optional, as needed and affordable)
* stat potions @24000GP
* mage book 5 @30000
* ring of Free Action
* ring of CON/INT
* ring of resist poison

Other useful purchases of equipment that sometimes show up in the ordinary shops are boots of speed, armor/shield of resistance, gloves or boots of Free Action.

Quote:

Originally Posted by Petoften

Now there are a lot more heal potions for sale - serious up from 3 to 21, and critical from 0 to 12 - is that normal or should I buy them all?

Right. Town books can be destroyed by fire. On the other hand, they can also be dropped in the dungeon if you have cleared a vault and have extra loot you want to stash at home. Same for ?Recall, ?PD, basic ammo. Don't leave CCW, however, as there is no guarantee of finding it for sale.